Static Phase Converter?

Hi Guys,
Once again I am here with my hat in hand humbly requesting your assistance. As some of you know, I am in the process of purchasing a Colchester Circa
1960's MK 1 1/2 lathe. It has a two speed 5hp 3 phase motor. Will I be able to run it successfully on a static phase converter?
Thanks in advance for the help.
Regards.
Joe...
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JB, I'd say probably, errr welll, make that maybe. Do this: Get in touch with Phase-A-Matic, large maker of static phase converters. Be prepared to give them the name plate information from the motor.
Bob Swinney

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Thank you for the advice, Robert.
Joe

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Joe
I am pretty sure you would be content with the performance of a lathe at home with a 5 HP 3 phase motor powered with single phase. You probably wont be content with its performance if you intend to run it loaded over about 4 HP for extended periods. I'm impressed with the ability of a lathe like that being able to reverse quite quickly.
Jerry
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Jerry,
Thanks for the help. I don't think I'll be loading it up over 4 HP, especially for long periods of time. My other concern is whether the two speed motor will work with a static converter. Some say yes, some say no and some say maybe.
Thanks again.
Joe...
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Reversing could get interesting. That can put a lot of stress on a phase converter. I've had the situation where a small rotarty would reverse instead of the lathe, a situation that could really make your day.
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Paul Amaranth wrote:

You could get around this simply by pausing with the switch in the off position until the spindle stops, then applying the power in reverse, right?
Chris
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right?
True, but the value of instant reverse is lost. There are times when that feature is very valuable to the guy on the machine. Tapping a hole with a tap in the spindle comes to mind. Failure to reverse instantly could prove expensive.
Harold
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    Thus eliminating the "reverse it quite quickly" which was promised about four articles back-thread. :-)
    If you want to do this, you want a hefty rotary phase converter. I don't think that a "static" phase converter as made by "Phase-O-Matic" could handle a two-speed three-phase motor very well. It will start well on one or the other speed, but not both.
    Enjoy,         DoN.
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d.com says...

Or in at least one instance (mine), though the HP of both speeds is within the range of the static converter, the motor will not start or run properly on either speed.
Ned Simmons
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My lathe also has a two-speed motor, rated at 5 HP on high speed and 3 HP on low speed. I could start it in either mode with a static converter -- but not with the same static converter, or at least not with the same capacitance.
There may be a way to trick a relay into the lathe's wiring so when the high-speed mode is engaged more capacitance is switched into the static converter.
Another option would be to manually switch the converter when you change speeds.
A large enough rotary converter, probably 10 HP idler, would start it in either mode.
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Can you not use the static to start a stand along motor with no load - spin that up and then the field and power in the windings will in turn drive the other motors and compensate on-the-fly.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Don Foreman wrote:

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Joe..save yourself some money and build a 7.5hp rotary converter. Even rope start works very well for this application. You should be able to find a good used motor for very little money (Id give you one if you were closer), or simply add a pony motor and spin it up then apply power to the big motor. Shrug..Im just about done with a 10hp pony motor run PRC that runs even my big Clausing 1501 (7.5hp) in full reverse/forwards applications, along with my big 3ph mig (though not at the same time <G>)
You DONT need the bells and whistles of a self starter, unless you absolutly want to.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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Gunner,
Thanks again for the advice. I too wish I lived closer to you. I have learned much from you already and I sincerely appreciate your effort in helping me.
Joe..

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Rotary phase converters are cheap and effective, build your own.
JB wrote:

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snipped-for-privacy@comcast.net says...

The only 3 phase motor I've not been able to run on a properly sized static converter is the 2 speed motor on my Feeler HLVH clone. Whether this is due to something common to all 2 speed motors, or peculiar to this specific motor, I can't say.
Bob's suggestion to ask Phase-a-Matic is sound advice.
Another option is a VFD, which is what I did on my lathe.
Ned Simmons
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you may find that a VFD costs about the same as a static converter (unless you happen to have the parts and plan on building it yourself) - look for a used one

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    Hmm ... a VFD is not likely to work well with a two-speed three-phase motor -- unless you do all speed switching with the VFD. You're not supposed to put the switch between the VFD and the motor, as the voltage spikes from the switching can zap the output transistors of the VFD.
    Here is a place where I feel that a rotary converter (build-it-yourself) would be the better choice. Or -- you could limit yourself to one set of windings on the motor, and do all speed changing with the VFD. For extreme cases (where you *really* need the higher torque of the low speed, or the higher speed of the high speed), you can stop the motor entirely (using the VFD's controls), switch to the other speed at the lathe's switches, and then start the motor back up with the VFD.
    Good Luck,         DoN.
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I don't think that is the case. All 2 speed motors that I have looked at have a much lower HP rating on Low speed than high speed. Usually it is less than 1/2. I would venture that a 2 speed motor runing on high speed but slowed down with a VFD will actually have more (or at least as much) HP as the same motor runing on low speed.
So in my opinion you can wire the lathe to only use high motor speed and then use the VFD to generate the low speed without any loose in motor torque.
Once you use a VFD you will love it. For example I was facing an 8 inch diameter disc. I set the VFD for 20Hz and geared the lathe for the speed I wanted for full diameter. As the toolbit works it way towards the center, I gradually increase the VFD frequency to increase the spindle RPM. It makes facing a big object so much faster and better.
chuck
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    Since the horsepower is a function of both the torque and the speed, this makes sense.

    That sounds good -- as long as the winding for the high-speed setting can handle the current at low speed operation.

    Excellent suggestion.

    And -- if you're doing a lot of the same part, you might even hook a rack gear on the cross-slide, and a pinion on a potentiometer, to have a result of a constant SFM as you face. This can also help eliminate chatter at certain speeds and radiuses.
    Enjoy,         DoN.
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